(1) Field of the Invention
The present invention relates to a method for preventing the formation of cellular gamma prime in cast nickel-based superalloys.
(2) Prior Art
In cast nickel-based superalloys, the cellular gamma prime precipitate is clearly undesirable. The cellular form of gamma prime, shown by the circled sites in FIG. 1, is not broadly known. In some cast nickel-based superalloys, it has been observed after hot isostatic pressing (HIP). Once formed, the gamma prime precipitate is difficult to dissolve as compared to the cuboidal form of gamma prime, which is familiar and essential for good performance under high temperature and stress. Creep rupture testing for material containing just low levels of cellular gamma prime have shown significant reductions in life. FIG. 2 illustrates these reductions in life.
Thus, there is a need for a method for preventing the formation of cellular gamma prime in cast nickel-based superalloys.